Evaluation of three estrus synchronization protocols and conception among dairy cattle at Njeru Stock Farm, Uganda

Abstract

Reproductive performance is still one of the most important factors that influence the profitability of a dairy herd, but there is a lot of poor reproductive performance in elite dairy herds. In extensive pasture-grazed systems, low conception and delayed breeding are mainly due to unobserved heats and variable ovarian cyclicity; therefore, structured hormonal oestrous synchronization protocols are essential to evaluate the time when heats occur and to maximize conception. This study aimed to assess and compare the efficiency of the single-agent and multi-agent hormonal synchronization on the onset of oestrous and conception in dairy cattle at Njeru Stock Farm, Uganda. An experimental study design was implemented using 27 (Holstein-Friesian) and 27 (Jersey) dairy cows that were divided into three treatment groups of 18 each: Treatment Protocol 1 (T1: PGF2α alone), Treatment Protocol 2 (T2: GnRH + PGF2α), and Treatment Protocol 3 (T3: PRID + GnRH + PGF2α). Treatment Protocol 3 gave a significantly higher oestrous response (83.3% (15/18 cows) than Treatment Protocol 2 (33.3% (6/18 cows)) and Treatment Protocol 1 (22.2% (4/18 cows)) (χ2= 15.343, df = 2, p = 0.000). The difference in oestrous response between Treatment Protocol 3 and Treatment Protocol 2 was highly significant (p = 0.009) and between Treatment Protocol 3 and Treatment Protocol 1 was highly significant (p = 0.001), while the difference between Treatment Protocol 1 and Treatment Protocol 2 was not significant (p = 1.000). With regard to Day 30 and Day 45 postAI, Treatment Protocol 3 resulted in a significantly higher conception of 77.8% (14/18 cows) than Treatment Protocol 2, 33.3% (6/18 cows) and Treatment Protocol 1, 22.2% (4/18 cows), with 2 cows in Treatment Protocol 3 conceiving during silent heat (χ2= 12.600, df = 2, p = 0.002). The pairwise comparisons showed that conception was significantly higher for Treatment Protocol 3 than for Treatment Protocol 2 (at P = 0.024) and Treatment Protocol 1 (at P = 0.003) and that there was no significant difference between Treatment Protocol 1 and 2 (at P = 1.000). The study revealed that multi-agent progesterone-primed synchronization (Treatment Protocol 3) was superior in increasing both oestrous onset synchrony and conception compared to single-agent and two-agent protocols, as it controlled follicular wave dynamics and overcame the limitation of ‘silent heat' during pasture grazing. The study recommends implementing Treatment Protocol 3 (PRID + GnRH + PGF2α) along with normal health and nutrition care to achieve maximum reproductive efficiency in dairy cows.